Antihunt electrical measuring system



Sept. 15, 1953 A. J. HORNFECK 2,652,524

ANTIHUNT ELECTRICAL MEASURING SYSTEM Original Filed Oct. 18, 1943 5Sheets-Sheet l inventor ANTHONY J. HORNFECK FIG.

Sept. 15, 1953 A. J. HORNFECK 2,652,524

ANTIHUNT ELECTRICAL MEASURING SYSTEM Original Filed Oct. 18, 1943 5Sheets-Sheet 2 FIG. 4

FIG. 7

INVEN TOR.

ANTHONY J. HORNFECK BY FIG. 2 4 0 A ORNEY I Sept. 15,1953 A. J. HORNFECKANTIHUNT ELECTRICAL MEASURING SYSTEM Original Filed Oct. 18, 1943 5Sheets-Sheet 3 'Imnentor ANTHONY J. HORNFECK m mml m attorney p 5, 1953A. J. HORNFECK 2,652,524

ANTIHUNT ELECTRICAL MEASURING SYSTEM Original Filed Oct. 18, 1943 5Sheets-Sheet 4 Fm'm'UTB 34 ix 87 3 ""1;}u mamm-- L Y 85 a a: is, w 0.0.INPUT A FIG. 8

FINAL ROTOR A POSlTlON V V 3 $9 Q 2 '5 PERIOD OF R8Ef- INITlAL ROTOR Aposmou T TIME UNBALANCE OCGURS H 9 0.6. SATURATING PATH 0F A.G. FLUXD.C. FEEDBACK A.C. OUTPUT 3nventor ANTHONY J. HORNFECK f 4 GttornegSept. 15, 1953 A. J. HORNFECK ANTIHUNT ELECTRICAL MEASURING SYSTEMOriginal Filed Oct. 18,1943

5 Sheets-Sheet 5 CIRCUIT FIG. I2

ANTI HUNT 0.6. INPUT STANDARDIZED D.C. VOLTAGE SOURCE FIG.. ll

lAA AAAA J POWER SUPPLY 3nventor ANTHONY J. HORNFECK Patented Sept. 15,1953 ANTIIIUNT ELECTRICAL MEASURING SYSTEM Anthony. J. Hornfeck,Lyndhurst, Ohio, assignor to Bailey Meter Company, a corporation ofDelaware Original application October 18, 1943, Serial No. 506,632.Divided and this application May 18, 1949, Serial No. 93,870

This invention relates to a system for measuring and/or controlling themagnitude of a variable, such as temperature, pressure, rate of fluidflow, position or displacement, although the variable may be of anychemical, physicaLelectrical; thermal or other characteristic.

, In accordance with my invention variations in a variable quantity,quality or condition are translated into variations in an electricaleffect, and this effect is then amplified solely through electricalmeans until sufficient power is available for doingusefulwork, such asmoving an indicator or other exhibiting means, or for regulating therate of application of an agent contributing to the production ormaintenance of the variable. a I

In devices of the same general type at present known wherein variationsin the variable are translated into variations in an electrical effectthe necessaryamplification is doneyat least in part, by mechanicalmeans. There are, there.-v

- fore, variations in ,magnitude of the variable translated intovariations in an electrical effect which is then translated into acorresponding mechanical movementsuch as the deflection of agalvanometer, and thenceusually the mechanical movement is translatedback into an electrical effect for operating the exhibiting bacon-- troldevice. Because of the small power available in the first electricaleffect such devices usually operate on a periodic or step by stepprinciple. That is to say, upon a change in the variable the exhibitingor control device is not continuously operated in correspondence withsuch change or changes, but periodically by means of a feeler mechanisman exhibiting or control device is changed an amount corresponding tothe amount of change in the variable during succeeding increments oftime. Such step by step and feeler mechanisms are well known in .theart.It is evident that such devices arenecessarily 6 Claims. (01. 318-28)The great majority of low level D.-C. measuring systems, such asthermocouple potentiometer recorders, use a galvanometer for detectingor measuring the D.-C. input. The galvanometer is a relatively fragiledevice and is affected by mechanical vibration and easily damaged byoverload or mishandling. Vacuum tube or electron amplifiers for lowD.-C. voltages have not been successful because 'of instability anddrift. A particular object of the present invention is to provideapparatus and a new method of detecting and amplifying small D.-C.voltages or currents. The present methodinvolve's the use of a device(which I term a reactor converter) which converts a D.-C. signal ofreversing polarity into a greatly amplified A.-C. signal of reversingphase. The apparatus includes a pair of iron core reactors andhas all ofthe sensitivity of a galvanometer as well as the sturdiness of atransformer. There are no delicate moving mechanical parts to Wear outor to be damaged.

The reactor converter produces a greatly amplified A.-C. output signalof reversing phase which issupplied to a phase sensitive electronicamplifier and motorcontrol circuit. In this way a thermocouplahaving anoutput of .only a few millivolts, is used to position a reversing motorwith no intermediate mechanical or moving'parts.

, ;'I'he"reversing motor may position anindicator complicated anddelicate anddo not correctly 7 exhibit the variable during-transientperiod's- My invention is, particularly concerned ,with the eliminationof all mechanical movements' between the sensitive device and theexhibiting or control device, leading to simplification and removal ofthe usual time delay, so that ithe device accurately exhibits themagnitude of. the vvariable even during transient periods. It is evidentthat many ancillary advantages will follow, among which may be mentionedas obviousthe elimination of wear of mechanical parts and the.eliminationf ofjtlie necessity ofperiodir': inspection and adiustmentto correct for inaccuraciesoccasioned by mechanical wear.

or recorder and atv the same time a potentiom eter for balancing thesystem, which may be of the null type.

A particular object of my present invention is in the provision ofan'anti-hunt electrical measuring system.

This application constitutes a divisionof my copending applicationSerial No. 506,632, filed October 18, 1943, now Patent 2,494,876, datedJanuary 17, 1950, to which reference may be had 1 for a more detaileddescription ,of the. circuit to which my present invention is applied.

Fig. 1' is a wiring diagram-including speed voltage feed-back from anauxiliary slidewire." Y

Fig. 2 illustrates a slidewire assembly. Fig. 3 illustrates a D.--C.measuring circuit with non-linear inverse feed-back.

Fig. 4 is a graph in connection with Fig. 3.,

Fig. 5 shows amodification of Fig. 3.

Figs. 6 and 7 are graphs in connection with Fig.5. Fig. 8 illustrates aportion of the circuit of a D.-C. measuring system embodying astabilizing feed-back from motorcontrol reactors.

Fig. 9 is a'grap'h' of operation, in connection with Fig. 8. l

Fig. shows a saturable core reactor construction for Fig. 8.

Fig. 11 illustrates a D.-C. measuring system usingphotoelectric-galvanometer converter with speed voltage feed-back froman auxiliary slidewire.

Fig. 12 is a modification of a portion of Fig. ll.

Fig. 1 is a diagrammatic representation of a high speed direct currentrecorder circuit using a speed-voltage feed back rrom'an auxiliaryslidewire. A thermocouple 21 is sensitive to the temperature of thefurnace l3 supplied with fuel for combustion through a pipe 44 under thecontrol of a regulating valve 45. The basic measuring circuit for thethermocouple 27 is de scribed in my copending application Serial No.

453,486, now Patent 2,529,450, dated November 7, 1950, and includes a.reactor-converter l5 and amplifier [6 for controlling a reversing motorI 8A which is adapted to position a recording pen 24.

In general the action or the reactor converter I5 is one of changing adirect current signal of given polarity into a greatly amplifiedalternate ing signal of given phase; and the ability of reversing thephase of the alternating current signal 180 when the polarity or sign ofthe direct current signal is reversed.

In a circuit of this general type :difliculty may be encountered becauseof the motor hunting about the balancing point. This instability may becaused by the inductive time lag in the reactor unit which produces aninertia or fly-wheel effect. In my copending application I provide 'afeed-back to the D.-C. inputcircuit in such a i direction as to opposethe input. Theeiiect of this feed back is to decrease the time lag inthe converter and to produce a momentary shift in the zero input .pointso that the D.-C. input circuit will be balanced before the true balanceis reached.

The anti-hunt circuit of Fig. 1 comprises broadly an inductive couplingdevice M whose primary is supplied with variable direct current from thepotentiometer circuit source and 1 whose secondary provides a feed-backto the input direct current saturating winding of the reactors'converter.15. "Current and voltage in the primary circuit is controlled "by theposition of. a contact arm 19 along a slidewire S said contact armpositioned by the motor l'flA'along with the slidewire contact 23, theindicator 2'4, and pilot 54. H r

The inductive coupling device M is in con struction in the nature of acoupling transformer, although it is inductively coupling 'twodirectcurrent circuits. The arrangement is such that when the voltage andcurrent in the primary circuit is variediby the motor 48A) the voltageand current in the output circuit is alsoyari'ed.

In a steady state there is no inductive "transfer effectbetweentheprimary and secondary. In other words, a variation .inthesecondary cir+ cuit is produced only upon change in voltage 'or cur-rentof the primary, is therefore proportional to rate of change in theprimary, and cpnses quently propor-tionalto rate of speed of the motorISA. r

The secondary voltage developed by the coupling device M is proportionalto the speed at which themotor IBA is positioning the slidewire contactS. A portion of thi's speed voltage is supplied in opposition to'theunbalanced voltage developed in the thermocouple-potentioineter circuit.Theeifect is to produce a dynamic or and running balance point ahead ofthe true static balance point. This tends to slow down or temporarilystop the motor so as to prevent over shooting and hunting and permitsmuch faster speed than would otherwise be'possible;

An auxiliary slidewire S, Whichmay be mounted on the same hub as themeasuring slidewire 23, is supplied with direct current voltage from thesource 15. The voltage then supplied to the primary of the couplingdevice M depends upon the position of the contact 19 relative to theslidewire S, while the secondary voltage is proportional to the rate ofchange of contact position; consequently is proportional to the motorspeed. Such an arrangement of slidewires is illustrated in Fig. 2wherein the motor rotor 46 may be provided with necessary gear reductionand drives an insulating hub 16 carrying on its periphery the slidewiresS and 23; as well as a cam 11. The indicator arm 24 may be positionedfrom the cam 11-, while contacts", l9 engage the movable slidewires 23and 'S respec tively.

The action of this speed voltage-feedback may be mathematicallyexplained as 'followsE If R1 is large compared with Li and M, the vol;tages a ei r=a ccnstantc speed 1 In Fig. "3 I illustrate "a directcurrent measuring system such as shown r g: o r wearers-sea; tionedPatent 2 529,450 but additionally including a non-linear inversereed-back 'l'he'jpurpose of this circuit is tolimit the build-.upioitil-skim: balanced current or voltage) supplied tropism potentiometermeasuring circuit to} li'ejreactoi, converter is. This is to preventshift "in. null point crpossible dama'ge'to the reactor con-f vertercaused by a rapid 'anuiarge change.i ,"rhe feed back also has m feirectr ma fsin it'ri stability oithesystemQ A non-linear resistor'xl incarbide type which: has fa. when low voltage "isapplied such a directionasto oppose the input.

coupling device M of Fig. 1.

resistance decreases at a very rapid rate as the voltage is increased.For small changes the feedback will be negligible and no appreciablereduction in sensitivity will result. For larger changes the feed-backwill become much greater and will limit the input currentto theconverter to a safe value, since the voltage er is always in Fig.4,expresses this graphically.

Copper oxide or a similar type of polarizing resistor may be usedinplace of silicon carbide.

To make such a unit independent of polarityit is necessary to use twocomponents as graphically indicated in Figs. 5, 6 and 7. v

Fig. 8 represents a further embodiment of my invention in connectionwith a part of a complete circuit. For example, referring to Fig. 3, Ihave indicated terminals 84,, 85,, 86 between the motor control tubesand the saturable reactor control of the capacitor-run motor [8A. InFig. 8 I omit, for the sake of simplicity, a duplication of thepotentiometer circuit as well as the reactor converter l5 and amplifierit. I show a feed-back arrangement to the D.-C'. input of the reactorconverter Hi from the saturable core reactors which are controlling themotor [8A responsive to an amplifier l6 and motor control tubes 36, 31.

To this circuit has been .added a stabilizing feed-back including twocoils 81., 88 wound around the'center leg of the motor control reactors5B and 5| in addition to the saturating D.-C. winding 84' or 85'. Thesecoils 81, 88 carry direct current and are connected inseriesso that theinduced voltages are additive. .A portion of this totaljvoltage isapplied to theinput circuit in such a direction as to accelerate thechange. Assuming that reactor X is saturated and that themotor'isdrivingthe potentiometer contact to balance from one direction. The D.-C.current in X will begin to decrease as the input to the'reactorconverter decreases while the D.-C. current in Y will begin to increase.This, change of current in X and Y will induce voltages in the windings.81, 88 of X and Y in accordance with the equation: :1 a

where M is the mutual inductance and iis the D.C. current.

The total voltage applied to the input circuitwill beproport:ional tothe sum of the two induced voltagesz' W i newe -mg and will oppose theoriginal unbalance from the measuring circuit. -Thiswi11-tendito slow adown or stop the motor before the truebalance is reached andwill preventexcessive overshooting or hunting. On theother hand, if the system isassumed to be in balance and a small change in the D.-C. input voltageoccurs, the induced voltage'will be in' 'sucha direction as to supply afeed-back voltage which will aid the original unbalance." This willaccelerate the motor faster than would otherwise occur and the speed ofresponse of the system will be increased. e

The arrangement is similar in theory to that described in connectionwith the inductive Winding 84' carries direct current saturating controlfrom the I rent Upon change in direct current value through the winding84 there is induced in the winding 81 a direct current whose magnitudeand polarity is determined by the direction and magnitude of change inthe voltage through the winding 84'. Under a steady state of voltage inthe winding 84 there is no direct current voltage -in the winding 81. Itis only upon change in voltage in the winding 84' that a voltage isinduced in the winding 81, and it is induced in a direction dependingupon the direction of change, i. e. whether the voltage in 84 hasincreased or decreased. The magnitude of the induced voltage in thewinding 81 is determined by the rate of change in voltage in the winding84'.

The direct current voltages in the circuit including the windings 81, 88in series are additive. When the motor 18A is to be rotated, then thesaturating current in winding 84' will increase (for example) while thesaturating direct current-in the winding decreases. The increase insaturating voltage in 84' produces a voltage in 87, while the decreasein saturating current in 85 produces a voltage in winding 88.

It will be noted that this feed-back couples the output circuit with theinput circuit in a regenerative fashion somewhat similar to certaintypes of vacuum tube oscillators. If thefeedback voltage is ofsufficient magnitude, self-oscillations can be induced in the systemwhich will keep the motor constantly in oscillation even at balanceconditions. By proper adjustment this oscillation can be held at a smallenough amplitude so as to just take up thebacklash in the gears and notenough to cause any motion of the potentiometer contact arm on theslidewire. By keeping the motor rotor quivering constantly thesensitivity of the system is greatly in creased, since static frictionof the motor bear ing. does not have to'be overcome before the motorbegins to position the potentiometer slidewire. Theslightest unbalanceof the measuring circuit swill unbalance the rotor-oscillations so thatthere will be an average motion of 'the potentiometer slidewire to'rebalance the system. This action is clearly shown in Fig. 9; Theconstruction of-the saturable core reactor X (or reactor Y) may be asillustrated in Fig. 10 comprising a three legged core' having the-A.-C.'output winding comprising two coils'on the outer leg connected in seriesand with the D.-C. input coil 84 and the feed-back coil 81 on the centerleg. r

The feed-back circuits illustrated inFigs. 1-10 inclusive, and describedin; connection therewith, are not limited to use in connection with there actor converter l5. Fig. 11 shows a circuit-using a vacuum tubeamplifier; motor control'circuit and feedeback systemj such as is showninjliigj. 1.but employing a photosensitive AgCgDagl (porn verter. g I;

Referring to Fig. 11; at balance equal'light falls. on the photo tubesPiand P2 so that the bridge circuitliof which thesetubesare a part)isbalanced. E and E2. are zero and the motor remains stationary, If achange in D..C input occurs the measuring circuit becomes temporarilyunbalanced and a voltage input to the galvanom-T eter G causes itsmirror to deflect. 'As a result the light falling on the photo tubes isunbalanced and a pulsating voltage appears across the output resistorR1. Since the vacuum tube amplifier is coupled through the condenser 89only the alternating component of the pulsating voltage E1 will appearacross Hz. This voltage is amplified and selectively controls reactors Tand U to cause the motor Isa to rotate and rebalance the measuringcircuit. Here, as in Fig. 1, I provide a direct current measuring systemincorporating speed voltage feed-back from an auxlliary slidewire and inconnection with a photoelectrie -galvanometer converter.

I have not felt it necessary to further complicate the drawings byduplicating the indicating or recording mechanism in the later describedfigures, although it will be appreciated that a primary purposeof thecircuit is to measure and provide a visual indication, as well asperhaps a permanent record, of the temperature or other variable whichhas produced the direct current, or change in direct current, which isto be measurod. Furthermore, of course the motors l8 and "a may be usedto control as has been described in connection with earlier figures ofthe drawing. Furthermore, the circuit arrangements are not limited tothe use of the capacitorrun type of motor, but may be equally as welladapted to opposed field motors, direct current In Fig, 1.2 I show amodification of the total circuit illustrated in Fig. 11 wherein theportions of Fig. 11 below and to the right of terminals 90, 9! andmechanical connections 92,

83 are not duplicated in Fig. 12. There is a somewhat simplifiedrecording system in which the amount of light falling on photo cells P1and P2 controls the flow of current through R1 and R2 and consequentlythe grid voltage of tubes V1 and V2. It more light falls on P1 than onP2 then V1 is made more conducting than V2 and reactor '1 passes currentto actuate the motor I So. This circuit difiers from that of 1.1 in thatdirect current voltage is applied to the anodes of the photo tubes P1and P2 and to the plates of the amplifying tubes V1 and V2 which controlthe satin-able reactors T and U.

- It will be apparent that I have illustrated and described certainpreferred embodiments of my invention but that I am not to be limitedthereto as many substitutions of equivalent apparatus and circuits maybe used without destroying the intent and novelty of my invention.

What .I claim as new, and desire to secure by Letters Patent of theUnited States, is:

1.- A .balanceable electrical network including ln combination, areactor converter having means for converting a low-level direct currentsignal of reversible polarity into an amplified alternating currentsignal of reversible phase, a source or alternating current for theconverter, a signal circuit including a source of low-level directcurrent and a connected resistor, electronic means selectively sensitiveto the alternating current output signal of reversible hase, areversible electric motor selectively actuatedby said electronic means,means positioned by said electric motor to balance said networkfollowing an unbalance thereof caused by variation in said directcurrent signal, and a non-linear inverse feed-back circuit electricallyenergized from the output circuit or said electronic means andsubjecting said resistor in the input circuit of said converter to avoltage modifying said low-level direct current signal;

2. The combination or claim 1 wherein said non-linear circuit includes asilicon carbide resistor having a high resistance when low voltage isapplied across it and whose resistance decreases at a very rapid rate assaid voltage is increased.

3. The combination of claim 1 wherein said non-linear circuit includes acopper oxide or similar type of polarizing resistor.

4. A balanceable electrical network including, in combination, a sourceof variable electronictive force to be measured, a motor adapted to oerate in accordance with the magnitude of said force, means responsiveto said magnitude operating to produce a control voltage for said motor,means positioned by said motor to balance said network following anunbalance thereof caused by a variation in said electromotive force, aresistor in circuit with said source producing said variableelectromotive force, a feed back circuit energizing said resistor tooppose the electromotive force from said source and including anon-linear resistor subjected to said control voltage. I

5. A system including means for producing a variable E. M. F. to bemeasured, a device having inertia and adapted to operate in accordancewith the magnitude of said E. M. R, means re sponsiv-e to the magnitudeof said E. MQF. riperatlng to control said device and producing a secondE. M. Frvarying in value with the operation of the device, means forintroducing into the system from the second E. M. F. an E. M. F;opposing the E. M, F. to be measured, said last mentioned meansincluding an element whose resistance varies with the E. M. F. appliedthereto.

6. The system as defined in claim 4 in which the means to produce acontrolvoltage for the motor comprises a pair of opposite A.-O.enetg'ized electron tubes each having a cathode load resistor, saidfirst mentioned resistor being connected to shunt the cathode loadresistor of the operating tube and :said now-linear resistor beingconnected in the circuit between said cathode load resistor and thefirst mentioned resistor.

' ANTHONY J. HORNFECK.

References Cited in the me of this patent UNITED STATES PATENTS,

Date

2,561,747 Merrill et a1. July 24, 1951

